Diamine compounds are widely used as a raw material or a crosslinking agent for thermosetting polymers or polycondensation polymers such as polyamide, polyimide, epoxy resin, and polyurethane. Fluorene has a fused ring structure composed of three rings and has a high planarity of the molecular structure. By allowing such a diamine compound to have a fluorene skeleton, properties derived from the high planarity of the fluorene skeleton are expected to be given to polymers formed using this compound as a raw material or a crosslinking agent.
The carbon atom located at the 9-position in the fluorene skeleton is the carbon atom of a methylene group, which has a higher reactivity compared to the other carbon atoms in the skeleton. Therefore, conventionally, a number of diamine compounds (see Patent Literatures 1 and 2) that have a fluorene skeleton in which substituent having amino group is bonded to the carbon atom at the 9-position in the skeleton, such as 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, and 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, are synthesized and commercially available. Hereinafter, the 9-position, the 2-position, and the 7-position in the fluorene skeleton may be abbreviated simply as “the 9-position”, “the 2-position”, and “the 7-position”, respectively, by omitting the phrase “in the fluorene skeleton”.